An ink cartridge stores ink to be supplied to an inkjet recording device (inkjet printer). The ink cartridge is provided with an ink storage chamber that stores ink and an ink supply port that supplies ink from the ink storage chamber to the inkjet printer. The ink supply port may also function as an insertion port for an ink extraction tube. When the ink cartridge is not mounted to the inkjet printer, the ink supply port is closed by a valve so that ink will not leak from the ink cartridge.
Mounting the ink cartridge to the inkjet printer is performed by pressing the ink cartridge toward the inkjet printer. In the inkjet printer, a hollow ink extraction tube is protrudingly arranged. When the ink cartridge is mounted to the inkjet printer, the ink extraction tube engages the valve that closes the ink supply port of the ink cartridge, and the ink supply port is opened. By opening the ink supply port, the ink storage chamber and the ink extraction tube are permitted to communicate with each other, and ink is supplied to the inkjet printer via the ink extraction tube.
JP-A-2001-113723 discloses an ink cartridge including a coil spring that presses a valve toward an ink supply port (insertion port for an ink extraction tube). The coil spring closes the valve, and thus the ink supply port when the ink cartridge is not mounted to an inkjet printer. The ink supply port is opened when the valve is lifted by insertion of the ink extraction tube against an urging force of the coil spring. When the ink cartridge is mounted in an inkjet printer and the ink extraction tube is inserted into the ink supply port, ink can be supplied from the ink cartridge to the inkjet printer via the ink extraction tube.
In particular, as shown in FIG. 2 of JP-A-2001-113723, a cylindrical portion 8 includes a constricted portion 32 having a diameter smaller than an outer diameter of an ink extraction needle 104. The constricted portion 32 is expanded by insertion of the ink extraction needle 104 and forms a fluid-tight seal with the periphery of the needle 104. On an ink chamber side surface of the cylindrical portion 8, a convex portion 34 is provided, surrounding the periphery of the constricted portion 32. An ink supply port 6 is closed when a valve body portion 40 contacts the convex portion 34.
However, in the ink cartridge disclosed in JP-A-2001-113723, when the ink extraction needle 104 is inserted to the constricted portion 32, friction with the ink extraction needle 104 during insertion causes the convex portion 34 to be lifted toward the ink chamber side, and the convex portion 34 maintains contact with the valve body portion 40. Therefore, to open the ink supply port 6, a valve body 10 must be pushed up by a greater amount than the convex portion 34. Thus a large stroke amount is required to open the ink supply port 6.